System for controlling pressure by acoustic means

ABSTRACT

A system for controlling pressure in a container, for example the carburetor of an internal combustion engine, from a periodic acoustic source, for example the intake or exhaust of the engine or a selected engine component where the alternating pressure varies only slightly according to engine speed where it is desired to modify the slope of a fuel richness curve over a wide operating range. The system is characterized in that it comprises a conduit connecting the container chamber to the acoustic source, the pressure losses being different according to the direction of flow in the conduit.

United States Patent [1 1 Malphettes et al.

[ SYSTEM FOR CONTROLLING PRESSURE BY ACOUSTIC MEANS [75] Inventors: JeanMalphettes; Pierre Fontanet,

both of Versailles, France [73] Assignees: Regie Nationale des UsinesRenault;

Automobiles Peugot, France [22] Filed: May 17, 1973 [21] Appl. N0.:361,064

[30] Foreign Application Priority Data May 29, 1972 France 72.19147 [52]US. Cl 261/72 R; 138/44; 261/D1G. 67 [51] Int. Cl. F02M 5/08 [58] Fieldof Search 261/72 R, DIG. 67; 138/39,

[56] References Cited UNITED STATES PATENTS 2,732,835 1/1956 Hundt261/72 R FOREIGN PATENTS OR APPLICATIONS 769,648 3/1957 United Kingdom261/72 Oct. 28, 1975 Primary Examiner-Donald R. Schran AssistantE.\'aminerZ. R. Bilinsky Attorney, Agent, or Firm-Strauch, Nolan, Neale,Nies & Kurz [57] ABSTRACT 4 Claims, 2 Drawing Figures us. Patent 'Oct.28,1975 Shee't1of2 3,916,020

US. Patent Oct. 28, 1975 Sheet 2 of2 3,916,020

SYSTEM FOR CONTROLLING PRESSURE BY ACOUSTIC MEANS BACKGROUND OF THEINVENTION This invention relates to a method and apparatus forcontrolling pressure in containers from a periodic acoustic source.

It is well-known that a periodic acoustic phenomenon producesalternating pressure waves. It is also known that in heat engines, andparticularly internal combustion engines, there are a large number ofsources of pe riodic noise and that there are also pressure controlproblems, particularly as regards metering of the airfuel mixture in thecarburetion of internal combustion engines.

This invention utilizes the periodic acoustic phenom ena produced bythese engines or other acoustic sources to control the pressure incontainers where it is required to effect a pressure correction.

Furthermore, in internal combustion engines used in motor vehicles, itis well-known that carburetion is frequently disturbed by acousticphenomena produced by the engines. This invention proposes moreparticularly to obviate this type of disadvantage by making use of theacoustic phenomenon which produced the disturbance, in order to correctthe effects of the latter.

The static positive or negative pressure increases rapidly with thealternating acoustic pressure and depends generally on the geometricfeatures of the container system, the value of the ratio of the pressureloss coefficients, and the frequency of the alternating acousticpressure of the periodic source.

SUMMARY OF THE INVENTION According to the invention, a pressure controlis effected in a container, such as the float chamber of an internalcombustion engine carburetor, from a periodic acoustic source byconnecting the container to the acoustic source by means of a conduitconstructed so that the pressure losses differ according to thedirection of flow through the conduit.

More specifically the conduit used in this invention is constructed sothat the ratio of the pressure loss coefficients in one direction andthe other direction is dif ferent from 1 so that the alternatingacoustic pressure passing through the conduit and originating from theperiodic acoustic source produces a static positive or negative pressureinside the container depending upon the value other than I of the saidratio.

A further object of this invention resides in providing a system forcontrolling pressure in a container from a periodic acoustic source bymeans of a conduit connecting the container to the acoustic source andso designed that the pressure losses inside the conduit differ accordingto the direction of flow inside the conduit.

Another object of this invention is to provide a control conduit for thesystem of the preceding object wherein the interior of the conduitcomprises at least one air jet of the venturi type.

Still another object of this invention is to provide a control conduit,the inner wall of which comprises a series of steps of differentdiameters thus producing a very appreciable pressure loss in onedirection and a small pressure loss in the other direction.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects will appear from thefollowing description and appended claims when read in conjunction withthe accompanying drawings wherein:

FIG. I is a diagrammatic section showing a first embodiment of theinvention connecting a carburetor float chamber venting system to theintake of an inter nal combustion engine; and

FIG. 2 is a diagrammatic section ofa second embodiment of the inventionconnecting a carberetor float chamber venting system to the exhaust ofan internal combustion engine.

Referring to the drawings, the air inlet passage 1 and its associatedventuri 2 are connected at one end to the air filter 3, of the periodicacoustic sources of an internal combustion engine, and at its other endto the intake manifold of the engine. The chamber 4, the float chamberof the carburetor, communicates with the jet 5 through the supplypassage 6, the jet 5 discharging at the constricted section of the airpassage 1.

Depending upon the position of the usual manual control butterfly valve(not shown in the drawings), conventionally situated downstream of airpassage 1, the flow of air through filter 3 and along the passage 1produced by operation of the engine creates a vacuum operative to inducea flow of fuel from passage 6 and atomization of the fuel to produce ametered mixture of the fuel from chamber 4 and air from the filter 3.

In the embodiment shown in FIG. 1, the top part of chamber 4 isconnected directly to the interior of air filter 3 by a smooth tube 7containing two air jets 8 and 9 of the venturi type. Jets 8 and 9 areoriented in tube 7 in such a manner that the pressure loss coefficientfor a flow of gas (air in this instance) through conduit 7 and jets 8and 9 in the direction of chamber 4 is less than the pressure losscoefficient of a flow of the same gas through conduit 7 and jets 8 and 9in the reverse direction from chamber 4 to the air filter 3. The ratioof the pressure loss coefficient in the direction of the acoustic source3 to the pressure loss coefficient in the direction of chamber 4 is,therefore, greater than unity in the case of FIG. 1. Upon operation ofthe internal combustion engine, the acoustic alternating pressure waveswhich appear in air filter 3 and which are transmitted through jets 8and 9 to chamber 4 result in a positive pressure in chamber 4 toincrease the flow of fuel introduced through conduit 6 to the airpassage 1.

As a result of this conduit and its association with filter 3 and floatchamber 4, the assembly enables the intake resonance effects which wouldnormally result in a mixture richness minimum, which is required to belimited, are counteracted. The correction provided by this invention isat all times proportional to the error, since the latter is a functionof the amplitude of the alternating pressure which itself modulates thevalue of the correction.

In other words, the disclosed and claimed invention is the creation of astatic pressure within a defined, closed space by connection of aconduit to a source of acoustic, dynamic pulsed pressure outside thespace, the conduit having assymetric pressure loss characteristics, thatis to say different pressure loss coefficients dependent on direction offlow through the conduit.

With this in mind, any one of ordinary skill in the art may obtain thedesired results of the invention merely by computing the pressure andresolving simple, known mathematical considerations.

Specifically, the parameters to be considered and resolved can be statedas follows:

Simple physics dictates that the formula for determining the pressuredifference for a flow directed from the closed space to the outside canbe stated:

M2 1, P PTII F Conversely, for a flow from the outside to the closedspace;

M2 P Pm "ET Restated:

M) P p 12 Pressure variations versus time according to a known adiabaticlaw may be stated:

Substituting and solving:

11 112. if P p Again, any one of ordinary skill in the art may obtainthe desired result merely by inserting determined values and resolvingthe derived equation.

DESCRIPTION OF ALTERNATE EMBODIMENT In the alternate embodiment shown inFIG. 2, the lid of float chamber 4 includes a conduit machined toprovide a series of diameters 11a, llb, and 110 which increase in theoutward direction. The venting conduit 11 fitted into the largest andoutermost diameter 11c,

may be connected through a flexible tube 12 to a point of the enginewhere a periodic acoustic source occurs, for example the engine intakeor exhaust or any suit able component where the alternating pressurevaries according to engine speed.

It will be apparent from FIG. 2 that the different diameters in machinedconduit 11, 110, Ill; and 11a, produce a pressure loss coefficient whichis higher in a direction of flow from chamber 4 to the acoustic source.

As in FIG. 1, the ratio of the pressure loss coefficient in thedirection of the acoustic source to the pressure loss coefficient in thedirection of chamber 4 is greater than unity and the periodic pressurewaves produce a positive pressure in chamber 4 so that the rate of flowof fuel is increased.

The system and method of controlling pressure in a container inaccordance with this invention may be used as illustrated particularlyin the case of internal combustion engines to obviate the disadvantagesdue to intake resonance which may produce a richness maximum or arichness minimum in the air-fuel mixture. According to the invention itis in fact possible to provide a carburetor chamber venting conduit sothat the rate of flow of the fuel is increased in the case where intakeresonance results in a mixture richness minimum.

Of course it would also be possible to provide a conduit in which theratio of the pressure loss coefficients would be less than unity, forexample by a reversal of jets 8 and 9 or the series of diameters 11a, 11b and 110, so that the alternating pressure waves would in that caseproduce a negative pressure in the carburetor float chamber. This couldbe used to obviate a richness maximum produced by an intake resonance.

The system according to the invention may also be used to modify theslope ofa richness curve over a wide operating range. If it is found ina given engine that the mixture richness is excessive over anappreciable range, for example at low engine speeds, the pressure lossin the float venting conduit may be so devised as to produce a negativepressure in the carburetor float chamber, this having the effect ofcompensating for the excess richness. In that case, the alternatingacoustic source will preferably be a component of the engine where thealternating pressure varies only slightly according to engine speed. Inthis way the negative pressure produced in the carburetor float chamberby means of the system according to the invention will be practicallyconstant irrespective of engine speed.

Since the negative pressure between the chamber and the air tube actingon the rate of fuel flow during normal operation of the carburetorincreases with engine speed, the compensating effect of the systemaccording to the invention will decrease when the speed increases, andin this way it will be possible regularly to reduce the richness of themixture at low speeds, while retaining the engine operation unchanged athigher speeds.

The system and the method according to the invention are of particularlyadvantageous application in controlling carburetion in internalcombustion engines and particularly in the carburetor float chamberventing conduits.

The invention may also be used wherever it is required to carry outpressure control in a container and it is possible to use a periodicacoustic source.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive. the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

l. A method of correcting carburetion errors in internal combustionengines comprising the steps of venting the carburetor float chamberthrough a conduit whose pressure loss coefficient is different dependingupon the direction of flow in the conduit and connecting the conduit tovent the flow chamber to a periodic acoustic source of the engine toestablish a preselected static pressure in the float chamber in accordwith the direction of flow through the conduit.

2. The method of claim 1 wherein the venting conduit is connected toestablish a positive static pressure in the float chamber.

3. The method of claim 1 wherein the venting conduit is connected toestablish a negative static pressure in the float chamber.

4. Apparatus for correcting carburetion errors in internal combustionengines comprising a carburetor including a float chamber and an intakepassage containing a venturi tube. a fuel supply passage leading fromsaid float chamber to said intake passage. a venturi jet disposed insaid intake passage to receive the fuel supplied through said fuelsupply passage and deliver the received fuel to the restricted area ofsaid venturi tube. an air filter connected to the intake end of saidintake passage. and conduit means interconnecting said float chamber andsaid air filter. said conduit means having a pressure loss coefficientin one direction of flow different from the pressure loss coefficient inthe other direction of flow to establish a preselected static pressurein said float chamber.

1. A METHOD OF CORRECTING CARBURETION ERRORS IN INTERNAL COMBUSTIONENGINES COMPRISING THE STEPS OF VENTING THE CARBURETOR FLOAT CHAMBERTHROUGH A CONDUIT WHOSE PRESSURE LOSS COEFFICIENT IS DIFFERENT DEPENDINGUPON THE DIRECTION OF FLOW IN THE CONDUIT AND CONNECTING THE CONDUIT TOVENT THE FLOW CHAMBER TO A PERIODIC ACOUSTIC SOURCE OF THE ENGINE TOESTABLISH A
 2. The method of claim 1 wherein the venting conduit isconnected to establish a positive static pressure in the float chamber.3. The method of claim 1 wherein the venting conduit is connected toestablish a negative static pressure in the float chamber.
 4. Apparatusfor correcting carburetion errors in internal combustion enginescomprising a carburetor including a float chamber and an intake passagecontaining a venturi tube, a fuel supply passage leading from said floatchamber to said intake passage, a venturi jet disposed in said intakepassage to receive the fuel supplied through said fuel supply passageand deliver the received fuel to the restricted area of said venturitube, an air filter connected to the intake end of said intake passage,and conduit means interconnecting said float chamber and said airfilter, said conduit means having a pressure loss coefficient in onedirection of flow different from the pressure loss coefficient in theother direction of flow to establish a preselected static pressure insaid float chamber.